This invention relates to a device for gripping and releasing rope and/or tape. In particular, this invention provides a mechanism which, when used in conjunction with a substantially conventional means of gripping rope and/or tape, enables loaded gripped rope and/or tape to be released easily and to be gripped easily as determined by controlled movement of the unloaded part of the rope close to or at a distance from the device. In particular, the effort required to release loaded rope is relatively small compared to the applied working load on the rope.
Conventional devices for gripping and releasing rope provide one or more clamps that act on the rope such that the clamping force on the rope is directly related to the applied load on the rope. For example, many conventional cleats use cams positioned on either side of the rope with the axis of rotation for each cam parallel to each other and perpendicular to the line or length of the rope. The rotation of each cam urges the cam forms to apply a gripping load to the rope, the gripping load being directly proportional to the applied load on the rope. The greater the applied load on the rope, the closer the cam surfaces move towards each other to apply a greater gripping force on the rope. This gripping force, together with the roughness and/or toothed form of the cam surfaces which contact the rope surface, provide the friction needed to overcome the applied load on the rope. Alternatively, some conventional cleats consist of one cam positioned on one side of the rope such that the cam rotates to push the rope against a relatively static surface on the other side of the rope. This surface is usually roughened and/or toothed to contribute to the friction needed to overcome the applied working load on the rope.
In order to release the rope from conventional gripping means such as cams, it is usually necessary to pull the unloaded or free end of the rope out of the gripping means in a direction which is substantially perpendicular to the line of the rope thereby dragging the rope across the surface of the gripping means. The amount of pulling force needs to be sufficient to overcome the friction between the gripping means and the rope, and is therefore relatively high as a proportion of the working load on the rope. This makes it difficult to release rope particularly when the applied working load on the rope is significantly greater than the available pulling force required to release the rope. On many conventional cleats, the available pulling force is limited by human hand grip and strength so that it can often be especially difficult, if not impossible, to release rope. Also, when the rope is dragged across the surface of the gripping means, the shearing forces between the rope surface and gripping means can cause serious damage to the rope particularly if the gripping means surface is roughened and/or toothed.
According to the present invention, there is provided a housing that is typically but not necessarily configured with a base and two sides through which rope or tape is allowed to pass. One end of the rope can be attached to a fluctuating or static applied load, and the housing is secured relative to the rope such that the housing is constrained not to move in the same direction as the applied load on the rope. A lever that is pivoted from the housing on an axis which is perpendicular to a line along the length of the rope, and which is parallel to the plane of the base of the housing such that rotational movement of the lever may be determined by movement of the rope passing through and extending from the end of the housing, the end being the end which is furthest along the length of the rope from the source of the applied load. A substantially conventional gripping member, such as a cam, is pivoted about an axis parallel to and positioned apart from the axis of rotation of the lever. The gripping member axis is able to move within a path constrained either towards or away from the rope, and the lever and gripping member axis is arranged such that the extent of rotational movement of the lever in opposite radial directions determines movement of the gripping member axis in two configurations in which the first configuration urges the gripping member axis and the gripping member towards the surface of the rope such that the gripping member compresses the rope against the base of the housing and grips the rope, and in which the second configuration allows the gripping member axis and the gripping member to move away from the rope thereby releasing the rope. The geometric and mechanical relationship between the lever and the gripping member axis is arranged such that the force needed to be applied at the lever by movement of the rope to move from the first configuration to the second configuration is small relative in the applied load on the rope, and the force needed to be applied at the lever by movement of the rope to move from the second configuration to the first configuration is also small.
Some embodiments of the housing may have only one side and further embodiments of the housing may have a top structure. While in typical embodiments, rope is compressed against the housing base, in some embodiments the housing may not have a base such that the rope is compressed against another component which is typically attached to the housing. In many embodiments, the cam and housing base may have a toothed (serrated) surface to assist in gripping the rope, and the cam may be urged by a light spring towards the rope. The cam as a gripping member is preferred in order to allow the invention to be used with a range of rope cross-sectional sizes. However, the invention could be configured to operate with any other suitable substantially conventional gripping means. Embodiments intended specifically for use with tape may use such other substantially conventional gripping means.
While a particular feature of the invention is its ability to allow easy release of loaded rope by operating the rope itself close to or at a distance from the invention, the invention may also be operated by other means such as by direct manual control of the lever to release and grip rope.